Microshear Bond Strength of Bioactive Restorative Materials to Dentin

Abstract

Purpose: To evaluate the microshear bond strength of bioactive restorative (BAR) materials to human dentin surface and estimate the clinical durability and serviceability of tested restorative materials Materials and Methods: Eighty dentin samples obtained from caries free human premolars and randomly divided into four groups (n = 20) according to application tested restorative materials First group (A) specimens tested direct application of bioactive restoratives BAR material to dentin without etching step. Second group (B) specimens tested for direct application of BAR material to dentin with etching step. Third group (C) specimens tested for direct application of bioactive base (BAB) material to dentin. The fourth group (D) specimens tested for direct application of nanofilled restorative (NFR) material to dentin with etching step, before application of tested restorative materials, a hollow cylinder (2.0 mm height/0.75mm internal diameter) was placed on the treated dentin surfaces. Tested restorative material inserted into the tube and cured. After artificial saliva storage for 5 days, the tube removed and microshear bond strength was determined in a universal testing machine at a crosshead speed of 0.5 mm/min. Data presented as mean and standard deviation (SD) values. Regression model using two-way Analysis of Variance (ANOVA) used in testing significance to evaluate the microshear bond strength of tested restorative materials. Results: It was found that group (B) BAR material bonded to etched dentin recorded the highest microshear bond strength mean value (12.18±1.39 MPa) followed by group (D) NFR material mean value (12.06±1.89 MPa) then group, (C) BAB materials mean value (9.96±1.27 MPa) while group (A) BAR material to unetched dentin recorded the lowest microshear bond strength mean value (9.88±2.11 MPa). The difference between all groups was statistically significant as indicated by one-way ANOVA (P=0.003>0.05). Tukey’s post-hoc showed non-significant (P>0.05) difference between (groups A and C) or (groups B and D). Conclusions: Saliva is a necessary component as calcium and phosphate supplement for proper bond strength of BAR to etched dentin. BAR and NFR have a good and clinically accepted micreoshear bond strength. BAB difficult to be used in open sandwich techniques. NFR proper adhesive selection lead to proper collagen encapsulation with qualified bonded interface.